【Objective】It is an essential prerequisite to understanding the environmental behavior of straw carbon in farmland soil to understand the decomposition characteristics of crop straw and the properties of dissolved organic matter (DOM) released. However, the information on straw decomposition characteristics obtained from relevant studies needs to be more comprehensive and requires further investigation. 【Method】In this study, the straws of corn, wheat, bean, and rape were laboratory incubated for 69 days. The two-dimensional correlation-Fourier Transform infrared spectroscopy (2D-COS-FTIR), ultraviolet-visible spectroscopy (UV-Vis), three-dimensional Excitation-Emission-Matrix Spectra (3D-EEM), and parallel factor analysis (PARAFAC) were employed to monitor the changes in the components of straw during decomposition (0–69 days), as well as the humification characteristics of their released DOM. 【Result】The results showed a double increase in corn, wheat, and corn straws during their decomposition period, and all four straws reached maturity at 65–69 d. At the end of decomposition, the mass loss rates of the four straws were 56.8 % (rape), 51.1 % (corn), 48.5 % (soybean), and 44.0 % (wheat), respectively. Although the decomposition order of different substances differed in the four straws, the decomposing intensity of functional groups on the surface of the corn, wheat, and rape straw exhibited the same order (C=O > O-H > -CH2 > -COO-) but the bean straw showed a different order. The dissolved organic carbon (DOC) content released by the corn, wheat, bean, and rape straws gradually decreased and was stable at 69 days of decomposition, of which the DOC content was 23.6, 12.2, 17.2, and 10.7 mg·g-1 biomass, respectively. During the decomposition, the SUVA254 value and aromaticity of DOM released from decomposed corn and soybean straws gradually increased, and the E2/E3 value gradually decreased. In contrast, those in wheat and rape straws showed a fluctuating trend. At the end of the decomposition, the aromaticity of DOM released from decomposed corn, wheat, bean, and rape straw was 20.58, 10.55, 17.45, and 8.32, as well as the E2/E3 value being 3.27, 4.29, 3.16, and 5.77. In addition, the aromaticity of maize and soybean straw DOM was higher than that of wheat and rape straw, and the E2/E3 value showed the opposite trend. The 3D-EEM results showed that though the DOM composition in the four crop straws varied, a similar conversion was observed from protein-like substances (I + II) to humic-like and fulvic-like substances (III + V). Four fluorescence components in the straw DOM identified by the parallel factor analysis model showed similar results. Finally, the humic-like substances (C2 and C4) comprised 35.0%–41.9%, and the fulvic-like substances (C1) accounted for 19.9%–42.9%. In contrast, the protein-like substances (C3) only accounted for 10.0%–29.4%. 【Conclusion】Our study revealed that the decomposition of straw and the content of its released DOM were influenced by the type of crop, while the substance degradation strength and transformation pattern remained consistent.